From the beginning of cable television service in the early 1950's until fairly recently, the predominant direction of information flow in cable systems has been from the headend to the subscriber. However, with the advent of pay-per-view and other cable services, it has become important to maintain the integrity of an upstream communication pathway from the subscriber to the headend to permit the ordering of services, and so on. The demand on the upstream communication pathway has continuously increased, with the addition of shopping, banking, Internet access, and other high-speed data communication services, including telephone services, being offered over the so-called “return path” to the headend. The bandwidth of the return path has been established in the 5 MHz to 42 MHz range. There are a number of sources of signal and noise in this frequency band other than return path communication sources. These other sources include, but are by no means limited to, amateur radio, citizens' band radio, machinery noise, home appliance noise, home computer clock signals, AM radio (which actually is slightly below the return path band, but nonetheless a trouble spot), and other electrical artifacts. It is often extremely difficult for the cable technician to determine where ingress into the cable system is coming from.